Voldemort structs no longer work?

[Iain Buclaw]

On 15 December 2012 19:45, H. S. Teoh <hsteoh at quickfur.ath.cx> wrote:

> On Sat, Dec 15, 2012 at 11:31:22AM -0800, Jonathan M Davis wrote:
> > On Saturday, December 15, 2012 19:50:34 Iain Buclaw wrote:
> > > On Saturday, 15 December 2012 at 18:38:29 UTC, H. S. Teoh wrote:
> > > > With latest git dmd:
> > > >   auto makeVoldemort(int x) {
> > > >
> > > >           struct Voldemort {
> > > >
> > > >                   @property int value() { return x; }
> > > >
> > > >           }
> > > >           return Voldemort();
> > > >
> > > >   }
> > > >   void main() {
> > > >
> > > >           auto v = makeVoldemort();
> > > >           writeln(v.value);
> > > >
> > > >   }
> > > >
> > > > Compile error:
> > > >   test.d(3): Error: function test.makeVoldemort.Voldemort.value
> > > >
> > > > cannot access frame of function test.makeVoldemort
> > > >
> > > > Changing 'struct' to 'class' works. Is this deliberate, or is it a
> > > > bug?  It is certainly inconsistent with Walter's article on
> > > > Voldemort types, which uses structs as examples.
> [...]
> > > Pretty certain it's deliberate.  No closure is created for nested
> > > structs to access it's parent, complying with it's POD behaviour.
> >
> > static nested structs don't have access to their outer scopes.
> > Non-static structs do. This reeks of a bug.
> [...]
>
> Found the reference in TDPL, §7.1.9 (p.263):
>
>         Nested structs embed the magic "frame pointer" that allows them
>         to access outer values such as a and b in the example above.
>         [...] If you want to define a nested struct without that
>         baggage, just prefix struct with static in the definition of
>         Local, which makes Local a regular struct and consequently
>         prevents it from accessing a and b.
>
> Ironically enough, Andrei in the subsequent paragraph discourages the
> use of such nested structs, whereas Walter's article promotes the use of
> such Voldemort types as a "happy discovery". :)
>
> Anyway, filed a bug:
>
>         http://d.puremagic.com/issues/show_bug.cgi?id=9162
>
>
If it is one, it's a bug in FuncDeclaration::getLevel.


-- 
Iain Buclaw

*(p < e ? p++ : p) = (c & 0x0f) + '0';
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